Thermal stability of NH4-chabazite

Abstract

The thermal stability of NH₄-chabazite has been examined by i.r. spectroscopy and thermal analysis combined with mass spectrometry. Dehydration occurs in two and deammoniation in four steps. Disregarding a very small water loss during deammoniation, dehydroxylation is completely separable from deammoniation and occurs in two distinct steps. Two OH stretching bands at 3540 and 3630 cm^–1 appear during deammoniation and could be related to distinct ammonium ions having bending vibrations at 1420 and 1460 cm^–1 respectively. The hydroxyls showing a band at 3540 cm^–1 are formed at lower temperatures and are less thermostable than other hydroxyls.